Dual Purpose Improved Conventional Munitions (DPICM) must have either a self-destruct capability or they must show dud rates not to exceed 1 in 500 as an operational requirement. To this end, several engineering studies were undertaken in an attempt to address the low reliability of the conventional M223 mechanical fuze. However, these studies did not change the basic design of the M223 mechanical fuze. Instead, they generally considered modifying the materials and the manufacturing processes to reduce the dud rate problem.
Conventional designs proposed the development of a hybrid electromechanical fuze which is relatively complex with approximately 40 to 50 parts, with a costly production line. In addition, the no-spin/low velocity operational environments of grenades jeopardize the fuze reliability. Several projectiles have unique operational requirements that the current fuze design might not meet readily.
Some of the concerns facing current self-destruct fuze designs are listed below:
(1) The threads between the arming screw and the weight can be overtorqued. PA1 (2) The fuze components may suffer collateral damage during ejection from the carrier. PA1 (3) The fuze may impact the ground at oblique angles and the firing pin might not provide sufficient energy to the detonator. PA1 (4) The fuze may operate poorly in a no-spin/low velocity environment. PA1 (1) It significantly improves the performance of traditional M223 mechanical fuzes by providing a redundant mode of operation, which adds a self-destruct capability and leads to a tactical destruction of the grenade at impact angles greater than 60 degrees (i.e., between 60 to 80 degrees) relative to the vertical, on all types of terrain. PA1 (2) It significantly simplifies conventional designs and the production process. It uses the main firing mode of the M223 fuze, and adds a few components to the M223 fuze, to add a relatively simple secondary mode of operation through a back up independent firing pin. These additional components can be made of readily available materials that are fabricated for example, by means of stamping, die casting, or precision molding techniques. PA1 (3) It solves the functional reliability problems when operating in a no-spin/low spin environment. PA1 (4) It uses a unique low cost mechanical design to provide a high functional reliability, in almost all operating environments. It uses an aerodynamic safety release (ASR) to function the secondary mode feature and to provide self-destruct capability. PA1 (5) Its components and assemblies are made of readily available materials and are fabricated from stampings, die casting and precision molds. PA1 (6) It meets all MIL-STD-1316D standards. PA1 (7) It is compatible with almost all grenade configurations. PA1 (8) It provides a self destruct delay of between 30-45 seconds. PA1 (9) It improves the fuze reliability with soft ground terrain impacts, and mitigates the problem of grenade impact at oblique angles of impact with the ground.
Therefore, there is a still unsatisfied need for a fuze which, among other features, solves the no-spin/low velocity environment, significantly reduces the number of components, improves productivity, and increases the operational reliability of the primary arming mode.
Several engineering studies were conducted in the past two decades in an attempt to address the low reliability of existing mechanical fuzes. Although these `mechanical only` solutions did improve the overall functional reliability of the fuze, there is still room for an improved design that fully addresses the no-spin/low velocity operational environment, and that significantly reduces the dud rate to the present ordnance requirements for self destruct fuzing of grenades.
A design that proposes a secondary self-destruct electrical mode of operation is described in U.S. Pat. No. 5,387,257. While the patented fuze provides an improvement in the relevant field, the activation of this self-destruct mode requires forces that are not available from no-spin/low velocity environment.